Electromechanical relays (EMRs) are used widely in a number of industrial applications, largely due to relatively low cost and/or small footprint when compared with other types of relays. These advantages allow a large number of relays to be deployed together to carry out complex functions, using standardized architecture for each of the various functions. The functions may include industrial control of machines, transfer machines, and other sequential control operations. Typically, such architecture is characterized by a control panel installed with a large number of relays whose contacts are easily converted from normally-open to normally-closed status.
An EMR typically comprises an electromagnetic coil with a soft iron bar, or armature. A movable contact is coupled to the armature such that the contact is held in its normal position by e.g. a spring. When the electromagnetic coil is sufficiently energized, by e.g. a user switching on the switch on the relay, a magnetic force overcomes the pulling force provided by the spring and moves the contact into an alternative position, such that the circuit is either now either broken or connected. When the electromagnetic coil is de-energized, by e.g. a user switching off the switch on the relay, the contact returns to and is held in its normal position by the spring.
Typically, systems may contain large electrical and/or electronic components which are controlled by EMRs. Such components may already provided with self-monitoring equipment and can raise “failure alarms” should the equipment malfunction. Such failure identification systems can help the maintenance crew to locate faults quickly. By locating the fault in time, the rectification process can be simplified and the maintenance crew may be able to restart the system within a short downtime.
However, EMRs are typically not equipped with such failure or fault monitoring equipment. Due to ageing of the system or any other reason, an EMR within the system may fail to execute the desired logic switch. In an application where hundreds of EMRs are connected together to form a system, any malfunction of one of the relays can lead to a complete system failure. When the system malfunctions, it can be significantly cumbersome for maintenance personnel to trace the faulty subsystem. For example, the steps for troubleshooting of the problem faced by the personnel include a first step of looking for a maintenance manual. Next, a wiring diagram would have to be examined. A trial and error method is then implemented to determine the faulty component. This trial and error method includes replacing a suspected faulty component (e.g. relay), before powering up and running the system to verify if the fault has been resolved. If the failure/fault is unresolved, the above process is repeated.
Thus, the troubleshooting process can be time consuming and can lead to prolonged system downtime if not resolved quickly. In instances where critical applications are involved, the prolonged downtime can result in catastrophic issues, causing user dissatisfactions.
Some EMRs come equipped with an ON/OFF LED indication. However, this is merely an indication that an EMR has been turned on with the magnetic coil within the EMR energised, without indicating that the desired contact switch (e.g. from Normally Open to Normally Closed) has occurred. In such instances, there is no way to quickly identify that the relay has failed to operate. In order to overcome this limitation, some EMRs are further equipped with an additional separate mechanical flag indicator, for indicating if the desired contact switching has occurred.
However, panels of EMRs are typically located in tight confined spaces where a maintenance personnel typically cannot easily access. Thus, a maintenance personnel may not be able to inspect the EMRs' mechanical flags easily. In addition, as such an EMR provides two separate information at e.g. different windows (one for indicating coil energisation and the other for indicating contact switching), the maintenance personnel has to check both windows of each EMR before determining which EMR is functioning incorrectly. This disadvantageously adds to the time taken to trouble shoot the system. Furthermore, with typically tens or hundreds of EMRs used in one panel, coupled with low light conditions due to constraints in actual work environments, the trouble shooting time taken may be significantly long.
Therefore, there is exists a need to provide a relay and a method for indicating a relay failure that seek to address one or more of the problems above.